In order to rotate the coaxial rotors in different or the same direction of rotation, earlier has normally been used two separate electrical motors. The first electrical motor rotates, typically using vee belt driving, the shaft of the first rotor in one direction of rotation. The second electrical motor rotates accordingly, typically using vee belt driving, the shaft of the second rotor in the opposite or the same direction of rotation.
The rotors are typically arranged within each other so that the separate rings of the rotors are allowed to freely rotate with respect to each other. The shaft assembly used to rotate the rotors is constructed so that inside a so called vertical pipe is beared the transmission apparatus for the so called upper rotor. Said transmission apparatus is rotated with a first lower motor. Outside said vertical pipe is beared the transmission apparatus necessary for rotating the so called lower rotor, wherein said transmission apparatus is rotated with a second upper motor. The material to be fed into the apparatus comprising the rotors can be fed from above the upper rotor, or alternatively, through the shaft driving the upper rotor, wherein the feeding is made from below.
The transmission arrangement described above requires relatively much space around the rotor apparatus. Particularly the use of two separate electrical motors requires a lot of space. Also it may be difficult to arrange the transmission from the electrical motor to a rotor into the centre of which material to be treated is intended to be fed through the shaft of said rotor.
Thus, the object of the present invention is to provide a new and improved impact mill, which is equipped with transmission machinery suitable for use in rotating two coaxial rotors in different directions or in the same direction with different speed.
Especially, the object is to provide a transmission machinery arrangement by use of which the aforementioned disadvantages are minimized or totally eliminated.
Thus, the object is for example to provide a transmission machinery arrangement which can be fitted in a smaller space than before.
Another object is to provide a more service friendly transmission machinery arrangement.